The present invention relates to optical elements and systems, and more particularly to a beam splitter wave guide apparatus capable of selectively filtering an optical input signal to provide at least two different optical spectra, and further operable to enable adjustment of the intensity of an output optical signal produced by the apparatus by selective rotational movement of an optical element of the apparatus.
In designing a dual-mode illumination system, the usual method for altering the output spectrum is to move filters in the path of the input light source. If the intensity of a bulb producing the output optical signal also needs to be adjusted (i.e., for arc lamps), then an iris, neutral density filter or other obstruction method is typically required to accomplish this task. This is because the bulb producing the optical input signal is not readily dimmable.
Accordingly, there exists a need for an apparatus and method which is capable of not only allowing one of a plurality of output spectra for an input optical signal to be generated, but also for a system and method which allows for adjustment of the intensity of the output optical signal.
More preferably, there exists a need for such an optical system and method as described immediately above which does not require the physical movement of filters into the path of the light source. Such an optical system would significantly reduce the cost associated with providing the dual spectra and intensity adjustment features. Such a system would also be more compact and capable of being manufactured even more cost effectively than previous dual-mode illumination systems.
The present invention is directed to a beam splitter wave guide apparatus and method. In one preferred form the apparatus comprises an optical element having an input end and an output end. The input end includes a first portion and a second portion circumferentially offset from the first portion. The first portion includes a filter capable of passing only a first optical spectra of an optical input signal impinging thereon, while reflecting the remainder of the optical signal. Conversely, the second surface includes a filter for passing only a second optical spectra and reflecting the remainder of the optical signal. A suitable device is included for rotating the optical element such that either the first surface or the second surface is positioned to be illuminated by the optical input signal.
In operation, when the first surface is aligned with the optical signal source generating the optical input signal, the first surface operates to pass an optical signal therethrough having the first optical spectra, while the second surface reflects this spectra to the output end of the optical element. When the optical element is rotated into position such that the optical input signal illuminates the second surface, then the second surface passes an optical signal having the second optical spectra therethrough. This spectra is then reflected off of the first surface towards the output end of the optical element.
It is a principal feature of the apparatus and method of the present invention that rotational movement while the optical input signal is impinging either the first surface or the second surface causes a variation in the intensity of the output signal produced at the output end of the optical element. Accordingly, the apparatus and method allows one of at least a pair of optical spectra to be selected by the selective rotational positioning of the optical element, as well as allowing for an adjustment in the intensity of the resulting output optical signal.
In a preferred embodiment the optical element further includes a third surface which is arranged between the first and second surfaces. When the input optical signal impinges the third surface, the optical signal passes therethrough and no output signal is produced at the output end of the optical element. In a preferred embodiment, the first and second surfaces are provided by beveled surfaces each having an appropriate filter formed thereon. The beveled surfaces cooperatively provide a chisel-type end to the optical element.
In an alternative preferred embodiment, the input end of the optical element comprises a conic shape. A first portion of the conic shape includes a first filter for passing only a first spectrum of the input optical signal and reflecting the remainder of the input optical signal. A second surface circumferentially offset from the first surface includes a filter that passes a second spectrum of the input optical signal but reflects the remainder of the input optical signal. Rotational positioning of the optical element therefore allows for the selection of an output signal having either the first or second spectrum. Similarly, controlled, rotational movement of the optical element while the input optical signal is illuminating either the first surface or the second surface allows the intensity of the resulting optical output signal to be varied. With this embodiment, portions of the input end in between the first and second surfaces are coated with an opaque coating to prevent any possible Total Internal Reflection (TIR) of the input optical signal to the output end.
It is a principal advantage of the apparatus and method of the present invention that no external mirrors, prisms or external filtering elements are required. Selectively coating surfaces of the input end of the optical element with suitable filtering material to produce the desired spectra and precisely rotationally positioning the optical element allows a desired spectrum to be selected, as well as a desired intensity, for the resulting output signal.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limited the scope of the invention.